Vaccinium is a large genus of ca. 450 species, mostly confined to the northern hemisphere. In Europe more than 30 species are cultivated as ornamentals or for their edible fruits (Gardner 1997). Four species are native in Belgium: Vaccinium myrtillus, V. oxycoccus, V. uliginosum and V. vitis-idaea. Most species, native as well as non-native, prefer shady, moist, often acidic substrates.
1. Corolla divided almost to base. Stems procumbent. Pedicels slender, ca. 3-4x as long as corolla. Fruit red. Plant evergreen === 2
1. Corolla divided at most ½ to base. Stems erect. Pedicels stout, at most as long as corolla. Fruit blackish blue or red. Plant deciduous or evergreen === 3
2. Leaves 6-18 mm long (largest leaves always at least 10 mm long), more or less obtuse at apex, margins not or only slightly inrolled. Fruit 10-20 mm wide === 2. Vaccinium macrocarpon
2. Leaves 4-8 mm long, acute at apex, margins inrolled. Fruit 8-10 mm wide (native) === V. oxycoccus
3. Leaves evergreen, margins inrolled. Fruit red (native) === V. vitis-idaea
3. Leaves deciduous, margins flat. Fruit blackish-blue === 4
4. Most leaves 30-80 mm long, acute at apex. Anthers without appendages === 1. Vaccinium corymbosum
4. Most leaves less than 30 mm long, rounded or obtuse at apex. Anthers with subulate appendages (native) === V. myrtillus and V. uliginosum
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Vander Kloet S.P. (2009) Vaccinium. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 8. Oxford University Press, New York-Oxford: 515-530.